Over on the beach, we find what looks like a rubber gasket, tumbling in the waves. While it might look like garbage, this is actually the way the moon snail reproduces. Let’s take a look first at this amazing predator that cruises past us just under our feet, hidden by layers of sand.
General info about the Moon Snail
I really love moon snails, partly because the shell (sometimes called a shark’s eye) is completely gorgeous!
These snails have a large foot that pulls them through the intertidal sands, and you’re most likely to notice a slightly raised track through the beach sand at low tide. If you look closely enough you can even see their little antenna-like structures and imagine a sort of face.
An Apex Predator who's an Expert Driller
They are ferocious predators as well, using a sharp tongue called a radula like a rasp to scrape away at the shell of their prey, lick-drilling and spitting an acidic substance until they can kill their prey and slurp-remove it from the shell. It’s this radula that creates those perfect jewelry holes you see on the beach. In this first photo below, we actually interrupted the moon snail’s lunch. As you can see, they’ll prey on bivalves and univalves alike.
Egg casings that look like gaskets
For some reason, I find a lot of these egg cases washing up in the winter. If you weren’t paying attention, you might dismiss this as a piece of plastic.
When the moon snails are ready to reproduce, the female lays her eggs onto a collar secreted of mucus and sand. According to the websites I could find about this, she then protects them with another layer of sand. The tiny eggs inside develop into planktonic larvae with moving cilia called veligers. At the very end of this post, you’ll find movies of moon snails pushing their egg collars as well as microscopic footage of veligers. (Thanks to the amazing work of other photographers and real scientists!) I did haul out a microscope to see the details of the collar layers and how they were cemented with proteins and embedded sand.
Microscope Views of Moon Snail Collars
Remnants of Larval Development
Sometimes when you find the collars, it seems like there are tiny shells attached to them. I think these are the remnants larvae, who have grown out of their casings and become free swimming. But just in case, I always leave these on the beach.
Longer Video for Observation
In case you want to explore these and watch them burrowning into the sand, here is a longer, non narrated compilation of my moon snail footage.
Other Videos you may like:
Here is a video of a similar snail pushing her collar to the surface:
Curious about Veligers? Here’s some real microscopic footage:
I found them fascinating. All this stuff that goes on around us, too small to see. In any case, it was a compelling visual for leaving sand collars on the beach.
